I like the idea very much of creating a simple gamebook but I have some question in trying to decide on whether to use Squiffy or the gamebook feature in Quest? Which gives you the ability to use more features? For instance it looks like the Quest gamebook lets you create really awesome scripts that let you easily choose things like playing YouTube videos or showing pictures or playing sound effects. Can you do all those things with Squiffy?

I'm not familiar with the gamebook feature in Quest, and would be interested to know more about it. But Squiffy is a fairly lightweight tool. The Squiffy documentation includes the following topics:

Sections and Passages
Using JavaScript
Turn Counting
Clearing the screen
Attributes
Embedding text
Tracking which sections and passages have been seen
Setting the start section
Setting the title
Continue links
Replacing text
Rotate and Sequence
Master sections and passages
Importing Files (command-line version only)
Customising HTML and CSS (command-line version only)

While it's possible to do extra stuff with JavaScript and HTML, you generally have to look up JavaScript and HTML tutorials to figure out how to do that (unless you already know JavaScript and HTML).

For me, Quest seems like an easy and quick way to create gamebook. I'm not that familiar with Squiffy.

I'm not that familiar with Squiffy so I may be biased, but Quest always seemed the clear choice to me. Squiffy is just for CYOA style games as far as I know, while Quest can make those too, or more complicated and immersive parser games, or anything in between.